Amorphous Formwork

ABSTRACT

The invention disclose a method and formwork for casting concrete or concrete like elements where said elements may have an amorphous shape, wherein the method comprises the following steps: —in a block of formable material having a size larger than the element to be cast, a model of the element is cut out, thereby creating an inner formwork; —an outer load bearing support structure having an inner size corresponding to the outer dimensions of the block is created; —the parts of the block not representing the model are arranged in the interior of the load bearing support structure, thereby creating a cavity corresponding to the model; —optionally reinforcement is arranged in the cavity; fresh concrete or other concrete like material is poured into the cavity and allowed to cure; —the outer load bearing support structure and the inner formwork are removed.

FIELD OF THE INVENTION

The present invention relates to formwork for casting concrete orconcrete like elements where these elements may have an amorphous shape.

BACKGROUND OF THE INVENTION

In the art of casting concrete or concrete like elements it iswell-known to cast elements which are round, circular, square,rectangular or any other well-defined linear or symmetrical shape. Thisfact has given, in particular concrete a relatively anonymous (boring)image, in that the constructions made from this material usually both bypeople skilled in the art such as architects, engineers, etc. and thegeneral public are conceived as being useful for only walls, floorslabs, pillars, tiles and a few other constructional elements which allhave the part in common, that they are designed with a relatively simplegeometry in order to provide for a relatively inexpensive constructionmaterial.

Fresh concrete, however, has the ability to flow and thereby fill outspaces which would otherwise, with other materials be very difficult tofill out, which in turn makes it possible to create shapes and formshaving an internal strength and integrity which could not be addressedby very many other materials. Until now the cost of formwork has made itprohibitive to contemplate such shapes for ordinary constructions.

From U.S. Pat. No. 4,887,789 is a form system as well as a method knownwhere a plastic core is used as an inner formwork in combination with aload bearing outer formwork. By appropriate shaping means, such as a hotwire, laser, water jet or the like a cavity is formed in the innerformwork. After the formation the inner formwork is placed inside theouter formwork, where after a hardenable material, such as concrete ispoured into the cavity. The method and formwork disclosed expresslystates that no intervening layer or material should be placed betweenthe inner formwork and the hardenable material to be placed inside thecavity in the inner formwork.

Another example is known from EP0440587 in which is described a formsystem comprising an outer member, for example made from cardboard.Inside the cardboard cylinder is arranged a plurality of form elementswhich along one side have been shaped to complement the innerside of thecardboard cylinder and on the other side side have been shaped such thatwhen the form elements are arranged inside the outer member, theinnersides of the form members will surround a cavity representing theshape of the concrete element to be cast. The formwork is especiallysuitable for casting polygonal pillar members. The formwork will in mostcases be for single use only in that in order to deform the oak concreteit will be necessary to destroy the outer cardboard member as well asthe form elements. It is, however, contemplated that a release agent ora foil may be used, but still the outer member will need to be destroyedin order to free the cast Concrete element.

A further example is known from GB 2397270. A mould system is describedwhere an outer stiff mould having a fixed shape is suitable toaccommodate an inner mould which may have more or less a random shape.The mould system is especially suitable for casting paving atones,tiles, bricks or blocks. The inner mould is provided with reinforcementribs such that an adequate support between the side of the mould againstwhich the concrete will be cast and the load bearing outer structure.The load bearing outer structure is constructed such that the innermould may be releasably fastened to the fixed outer mould in order toremove the cast concrete panel and/or the inner mould.

This aspect has, by the inventors of the present invention been foundinvolve problems in some of the areas where it is desirable to castelements, and has therefore necessitated improvements involvingsubstantial creativity. Particularly when casting elements which are notcylindrical, i.e. where the cross section is not formed by an infinitenumber of parallel lines, it was fairly impossible to utilise themethod, even when applying conventional release agents used extensivelyin the construction industry. The problems were further aggravated whenthe inner formwork was made from expanded polystyrene foam materials.The use of expanded polystyrene foam products is especially advantageousdue to low prices, very low weight pr volume unit and high/easyformability.

OBJECT OF THE INVENTION

The present invention therefore provides both a method for casting and aform work for casting concrete or concrete like elements where saidelements may have an amorphous shape. In this connection amorphous shapecovers a wide variety a shapes (symmetrical as well as asymmetrical) aswill be evident from the description with reference to the detailedembodiments, see below. Furthermore the invention is directed atproviding a method which is easy to carry out, at low cost, and wherethe finish on the manufactured elements is greatly improved compared tothe state of the art.

DESCRIPTION OF THE INVENTION

The invention accordingly provides a method which is new and inventivein that the method for casting concrete or concrete like elements wheresaid elements may have an amorphous shape, comprises the followingsteps:

-   -   in a block of formable material having a size larger than the        element to be cast, a model of the element is cut out, thereby        creating an inner formwork;    -   an outer load bearing support structure having an inner size        corresponding to the outer dimensions of the block is created;    -   the parts of the block not representing the model are arranged        in the interior of the load bearing support structure, thereby        creating a cavity corresponding to the model;    -   a release agent either in liquid form or as a foil or membrane        is arranged covering the cavity in the inner formwork;    -   optionally reinforcement is arranged in the Cavity;    -   fresh concrete or other concrete like material is poured into        the cavity and allowed to cure;    -   the outer load bearing support structure and the inner formwork        are removed and where the elements are sections of a larger        structure, and where templates defining end surfaces of the        elements to be joined are used, such that surfaces of two        adjacent elements to be joined, use the same template when the        model is being cut out of the formable material.

In order to be able to cut a model out of the formable block, the blockmust be of a size larger than the element to be cast. When the model iscut out of the block, care should be taken not to damage the formablematerial, in that the model as such is not interesting, but the cavitythat it leaves in the formable material is the part which will give theshape for the finished cast construction.

The inner formwork is therefore made up of the cavity created in theblock when the model of the element to be cast has been removed. In someinstances it may be necessary to partition the block of formablematerial in order to remove the model depending on the shape of themodel. The inner formwork will therefore consist of a number of partswhich will thereafter be assembled inside an outer load bearing supportstructure, where the size of the support structure corresponds to thesize of the block so that an efficient support for the block of formablematerial is created.

When the inventive method according to the invention is used for castingelements of a certain size or elements which are not entirelyornamental, it will be desirable to arrange a reinforcement inside theconcrete in order to be able to give the concrete the physicalcharacteristics which are normally associated with reinforced concretestructures.

Depending on the material from which the block of formable material ismade, the removal of the inner formwork from the cured concrete elementwill usually be carried out by firstly removing the concrete and theinner formwork from the load bearing support structure and thereafterremoving the inner formwork from the concrete element. In some instancesdepending on the material from which the formable material is selectedit may be difficult to remove the inner formwork from the cast elementand in these instances a suitable release agent should be applied to theinner formwork prior to casting the concrete. These techniques are verywell-known in the art of casting concrete in order to be able to releasethe formwork from the hardened concrete.

Although traditional substances may be used with some success, testshave shown that exceptionally good results are achieved with thefollowing substances, in particular when the inner form-work is madefrom a foam material or an expanded polystyrene material.

A traditional retarder was applied to the inner formwork before castingthe concrete. This substance, for example a simple sugar solution, madeit very easy to part the cast element from the formwork, and at the sametime had no effect on the formwork, such that the formwork was suitableto be reused. The micro-surface of the concrete element, however, wasrelatively large/open, and it is contemplated that elements manufacturedin this manner, should be used indoors or be treated, for example by acoat of paint, before exposed to an outside environment. An oil based onvegetables, such as for example oils derived from sunflowers, sesame,grapes, flax and the like is also usable. When a crisp white result isdesired, care shall be exercised when selecting the oil, in that the oilmay cause mis-colouring of the white concrete surfaces.

A suitable wax also showed remarkable results. A wax from X-Coating, aDanish corporation, sold under the tradename X-I 1000 proved veryusefull. A mixture of oil and wax was used where the oil was pure oilused for medical purposes containing 3% to 15% wax. The surfaces of thecast elements showed no signs of the release agent.

Also Vaseline, wood glue (PE glue), silicone, Latex and other substanceswere tested, but the wax solution was selected as the best, both withrespect to application, release and discolouring.

In addition to release agents in liquid form, also membranes and inparticular flexible membranes proved to provide very satisfactoryresults.

The method as well as the formwork is equally suitable for one-offconstructions and for the manufacture of elements on an industrialscale.

In a further advantageous embodiment of the invention the block is madefrom a poly-styrene based product and a hot wire is used for cutting themodel.

By selecting a polystyrene material it becomes very easy to shape themodel simply by pulling a hot wire through the polystyrene materialwhich will thereby melt and provide for an easy and very smooth cut.Furthermore, polystyrene based products are usually very cheap and verylight and as such easy to handle, and furthermore by selecting anappropriate, high quality polystyrene, a very smooth form surface may beachieved by this method.

The invention is also directed at a formwork for use in the inventivemethod where said formwork comprises:

-   -   an outer load bearing support structure, which support structure        has means allowing the structure to be disassembled, thereby        freeing    -   an inner formable structure, which inner structure defines the        outer shape of the element to be cast.

Further advantageous embodiments of the invention are set out in thedependent patent claims.

Below examples illustrating the inventive principle are described. Theexamples shall not however be construed or interpreted as having alimiting effect on the scope of protection, sought, but merely serve toillustrate how the inventive principle may be exploited.

DESCRIPTION OF THE DRAWING

FIG. 1 illustrates prior art formwork;

FIG. 2 illustrates a wall created using the invention;

FIG. 3 illustrates form elements used for the wall in FIG. 2;

FIG. 4 illustrates a block before being shaped;

FIG. 5 illustrates a template;

FIG. 6 illustrates a template arranged on a block;

FIG. 7 illustrates the assembly of the formwork;

FIG. 8 illustrates how the inner form is cut;

FIG. 9 illustrates how separate forms fit together for longerconstructions;

FIGS. 10 and 11 illustrate a further embodiment where the formwork isused in a very complex shaped construction.

FIG. 11 a-16 illustrate various methods of carrying out the invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is illustrated a traditional formwork used to cast theunderside of a staircase. Due to the flowing shape of the staircase itis necessary to build a rather complicated formwork in order to achievethis shape for the actual staircase. The traditional formwork asillustrated in FIG. 1 comprises a large number of latches 1 which arearranged side by side in order to create the form face. The bottom shapeis created by the latches 1 being shaped by plate members 2 arrangedalong the sides of the formwork. The plates 2 are bolted 3 to an understructure 4 in order to create a construction stiff enough to maintainthe shape of the formwork during the casting process of the concrete. Itis evident that this type of construction requires a substantial amountof labour and thereby becomes very costly.

The invention, however, provides a relatively cheap alternative to this,which furthermore may be able to provide much smoother transitionsbetween curved sections and therefore also achieve a far more pleasingresult with less effort and less cost.

Turning to FIG. 2 an example of a wall element 5 is illustrated. Thewall element has a substantial homogenous thickness which is created byhaving substantially parallel lines from the bottom of the wall to thetop of the wall, but apart from that the wall may be given any suitableshape. From FIG. 2 it is evident that both curves in the vertical aswell as the horizontal plane are possible, and also double curvature maybe achieved. The wall may furthermore be equipped with support sections6 which will help this particular shape to keep its balance on its own,but for practical purposes the wall element 5 will be placed on afoundation and fastened in a traditional way, e.g. with bolts, to theunderlying foundation structure. The wall as depicted in FIG. 2 may beachieved with a formwork as illustrated in FIG. 3.

In order to understand how the inventive formwork is made, the attentionis directed to FIG. 4. In FIG. 4 a block of a formable material 10, inthis example polystyrene is depicted. The block has a size, i.e. awidth, height and length larger than the object which is to be cast. Bymeans of a heated wire 11 in this instance connected by handle 12 to asource of electrical energy the heated wire may easily cut through theblock of polystyrene. The “cutting” is achieved by melting thepolystyrene as the wire is pulled through the material.

In order to ensure that the desired shape is achieved a template asillustrated in FIGS. 5 and 6 may be used. The template 13 is fastened ineither end of the block 10. The template 13 is decisive for the shape ofthe end of the element to be cast. Turning to FIG. 6 it is clear thatthe template 14 will provide for a different shape of the element to becast. By pulling the hot wire 11 as illustrated in FIG. 6 through theblock material 10 and arranging the hot wire through the material itbecomes possible to cut away part, of the block material 10 asillustrated in FIG. 6. From the exposed surfaces of the material 16 itis evident that the exposed surface has a curved shape both with respectto the longitudinal direction of the element to be cast and in acrosswise direction. This is achieved by the curvature 17 of an edge ofthe template 14 and by not tightening the hot wire completely, so thatthe friction/resistance created by the polystyrene block material 10 onthe wire, will create the longitudinal curvature of the exposed surface16. Should such shape have been created by traditional means it wouldhave been a very expensive and cumbersome process to create such ashape, and in this connection reference is made to the rather simpleshape illustrated in FIG. 1 which in spite of being a relatively simplecurved surface requires a substantial amount of work and craftsmanshipin order to create an acceptable shape.

Once the hot wire 11 has been pulled along the entire circumference ofthe template 14, the pieces 18, 19, 20 will be the inner formworkagainst which the fresh concrete will be cast. The part of the blockmaterial 10 between the template 14 in either end of the block is amodel of the concrete structure to be cast, but will not be used for theCasting process.

The inner mould sections are hereafter arranged in an outer load bearingsupport structure, where this load bearing support structure has aninner size corresponding to the outer size of the block material 10.

This is illustrated in FIG. 7 wherein the cut-away sections 18, 19, 20being the inner formwork are in the process of being arranged inside theouter load bearing support structure 21. Before the concrete is pouredinto the mould all the inner moulds are arranged and the outer loadbearing structure is closed in order to enclose the inner mouldscompletely except naturally for the upper opening through which theconcrete is poured. A very rigid and strong formwork is hereby created.

Turning to FIG. 3 the inner formwork for the wall as illustrated in FIG.2 is illustrated. The inner formwork consists of a front and back part30, 31 and for illustrative purposes the templates 32, 33, 34, 35 arealso illustrated. The inner moulds have been shaped by pulling the hotwire along the template 32 as illustrated in FIG. 8.

In FIG. 3 the corresponding inner moulds 30, 31, do not have endsections which correspond to the next consecutive element. This,however, may be solved as illustrated with reference to FIG. 9, whereinthe same template used in the first set of elements is also used for thesecond set. The first set of inner moulds 41, 42 is created as explainedabove by using templates and cutting with a hot wire through the blockmaterial. The template used on the face 43 of the inner mould 41 is alsoused for the next set of inner moulds 44, 45 so that the inner mould 45on one end surface is cut along the same template 43 as the first set ofinner moulds 41, 42. In this manner it is ensured that the inner mouldelements 41; 45 will create a smooth transition such that a continuouselement e.g. as illustrated in FIG. 2 may be created. The folio wing endface of the inner mould 45 is created by the template 46 which again isused for the adjoining set of inner moulds as already explained, and soon.

In FIG. 10 is illustrated an inner mould created according to theprinciples described above which inner mould 50 may be fitted inside anouter load bearing support structure 51. The elements cast in the innermould 50 are depicted in FIG. 11 and are mentioned here in order toillustrate the versatility and the wide variety of possibilities whichare possible with the inventive formwork according to the invention.With traditional formwork the structures as illustrated with referenceto FIGS. 2, 6 and 11 would have been so expensive that in tact it isvery likely that they would have been taken out of the projects had itnot been possible to manufacture them by using the versatile andrelatively cheap formwork system according to the present invention.

With reference to FIG. 11 a to 16 various embodiments of performing theinvention are illustrated.

In FIG. 11 a a membrane 47 made from latex or synthetic rubber,typically having a thickness of from a few tenths of a millimeter to afew millimetres is fastened to a frame 48. The membrane 47 is notpre-shaped, but is a straight flat membrane section. The size of theframe 48 is such that it may be supported on the upper ledge 49 of theload hearing outer formwork 50. The block of formable material 51, madefrom poly-styrene, is provided with a cavity 52 corresponding to thedesired shape of the finished cast element.

By placing the block 51 inside the formwork 50, and, superposing theframe 48 with the membrane 47 over the ledge 49, the formwork is readyto receive the concrete. The concrete is poured on the membrane 47,which thereby deforms to the shape of the cavity 52.

Once the concrete has set, it is relatively easy to remove and reuse themembrane 47.

Additionally the surface finish of the concrete element is very smooth,due to the surface characteristics of the membrane, in particular whenmade from Latex.

The embodiment illustrated in FIG. 12 corresponds to the embodimentdescribed with reference to FIG. 11 a. Only in this embodiment themembrane 53 is pre-shaped. When pouring the concrete the membrane doesnot need to stretch as much, and with this embodiment it is thereforepossible to make larger constructions compared to the previousembodiment. This embodiment also corresponds to the embodimentillustrated in FIG. 15, where an element having a limited cross section,but a relatively long shape is illustrated.

Alternatives to the embodiments described with reference to FIGS. 12 and15 are illustrated in FIGS. 13 and 16. Here the release agent is in theshape of a liquid 54. Preferably a mixture of oil, and wax is used as acoating on the inside of the cavity 52.

In FIG. 14 is illustrated an embodiment of the invention suitable tomanufacture surface elements. The formable material is sand 55, which isplaced inside the outer formwork 50. The upper surface of the sand 55will determine the surface shape of the element to be cast. The membrane47 will due to its stretchability and flexibility conform to the shapeof the sand 55, when the concrete is poured on top, of the membrane 47.

Above the invention has been explained with reference to a few detailedembodiments, but the scope of the invention shall not be construed asbeing limited by these examples, but should rather be limited only bythe scope of the appended claims.

Although the invention has been explained above with reference tospecific embodiments, the inventive principle may be achieved by other,not illustrated means and method steps. For example instead of manuallabour cutting the block material this may be carried out by industrialrobots. Industrial robots are great for repetitive processes and forprocesses which may be designed by for example an architect on acomputer and transferred to the robot which thereafter exactly createsthe design on the block. In such instances the templates may besuperfluous, in that the robot may work without such aids.

The inner formwork may also be preformed. For applications where a largenumber of identical amorphous elements are to be manufactured, it may beadvantageous to premanufactured the polystyrene foam elements, or useother suitable materials for this purpose, as the requirement to beingable to shape the inner formwork by means of a hot wire has beendispensed with.

A computer based design aid may be contemplated, where the softwareautomatically reserves a central zone for reinforcement, tension cablesetc, and sufficient concrete cover over the reinforcement, such that thedesigner is free to use the rest of a given cross section in order tocreate the desired shape.

1. Method for casting concrete or concrete like elements (5), where saidelements may have an amorphous shape, wherein the method comprises thefollowing steps: in a formable material (10) having a size larger thanthe element to be cast, a model of the element is cut out, therebycreating an inner formwork (18,19,20,30,31,41,42,44,45); an outer loadbearing support structure (21,50) having an inner size corresponding tothe outer dimensions of the formable material (51) is created; the parts(18,19,20,30,31,41,42,44,45) of the formable material not representingthe model are arranged in the interior of the load bearing supportstructure (21,50), thereby creating a cavity corresponding to the model;a release agent (54,47,53) either in liquid form or as a foil ormembrane is arranged covering the cavity (52) in the inner formwork(51); optionally reinforcement is arranged in the cavity; fresh concreteor other concrete like material is poured into the cavity and allowed tocure; the outer load bearing support structure (21,50) and the innerformwork (51) are removed and where the elements (5) are sections of alarger structure, and where templates (13,14,32,43,46) defining endsurfaces of the elements to be joined are used, such that surfaces oftwo adjacent elements to be joined, use the same template when the modelis being cut out of the formable material.
 2. Method according to claim1 wherein the formable material is a block made from a polystyrene basedproduct, and that a hot wire is used for cutting the model.
 3. Methodaccording to claim 1 wherein the inner formwork is pre-manufactured, andoptionally allowed to remain in contact with the concrete during thehardening process, whilst another set of inner formwork is arrangedinside the outer load bearing support structure.
 4. Method according toclaim 1 wherein a suitable release agent is applied to the formworkbefore casting, where the release agent is a liquid which is selectedamong one or more of the following: retarder, vegetable oil, oilbasedwax, Vaseline, PE glue, latex, synthetic rubber, silicone.
 5. Methodaccording to claim 1 wherein a suitable release agent is applied to theformwork before casting, where the release agent is a membrane or foil,where the foil is flexible and made from latex, or synthetic rubber,where said membrane or foil optionally is preformed.
 6. Formwork forcasting concrete or concrete like elements in the method according toclaim 1, where said elements may have an amorphous shape, wherein theformwork comprises: an outer load bearing support structure (21,50),which support structure has means allowing the structure to bedisassembled, thereby freeing an inner formable structure(18,19,20,30,31,41,42,44,45), which inner structure defines the outershape of the element to be cast, where said element has at least twosurfaces, and where at least one surface is manufactured by cuttingalong a template, whereby the inner formable structure has acorresponding shape; a liquid, foil or membrane release agent, coveringthe inner structure.
 7. Formwork according to claim 6 wherein the innerformable structure is made from a polymer-based lightweight foammaterial.
 8. Formwork according to claim 6 wherein the inner formablestructure is made from a castable material, and that the inner formworkis created by casting the castable material around a model of theelement to be cast.